US2286020A - Power transmission - Google Patents

Description

June 9, 1942. D. v. SMYTH 2,286,020

POWER TRANSMISSION Filed March 6, 1941 INVENTOR DAVID V. SMYTH BY i V ATTORNEY other as a fluid motor. The invention is more particularly concerned Patented June 9, 1942 rowan TRANSMISSION David V. Smyth, Waterbury, Conn., assignor to Vickers Incorporated, Detroit, Mich., a corporation of Michigan Application March 6, 1941, Serial No. 382,021

3 Claims.

This invention relates to power transmissions, particularly to those oi the type comprising two or more fluid pressure energy translating devices, one of which may function as a pump and anwith a hydraulically-operated, single-cycle, control mechanism of the type which may be initiated into operation by an impulse oil pressure fluid and will thereafter cause a predetermined cycle of operation to occur during which the control mechanism is unaflected by any subsequent accidental or intentional pressure impulses.

. Control mechanisms of this general character have been heretofore constructed and used with complete success. They have, however, required that the source of pressure fluid from which initiating pressure impulses are derived be such as to admit of the pressure source being bypassed I through the control device whenever an impulse is attempted to be applied while a cycleof op oration is taking place.

This has heretofore required a separate pump ior supplying fluid to the initiating circuit which could not be utilized for other purposes.

It is an object of the present invention to prot vide an improved single-cycle control mechanism of this character and in which means is provided for preventing bypassing of the pressure supply while a cycle is taking place in the event of an attempted restarting of the mechanism.

motor I, is provided for driving a pump l2 forming a source 01 fluid under pressure. The pump i 2 may be of any suitable type, the one illustrated being a duplex combination pump which is arranged to provide large and small volumes for rapid traverse and feed depending upon the pressure encountered in the delivery line. Such pumps are a standard article of commerce, for example, the Vickers VC type of pumpwhich incorporates the necessary control valves for shift- I ing between large and small volume output in accordance with delivery line pressure. The basic circuit for such a pump is illustrated, for example, in the Vickers Patent 1,982,711.

The pump is adapted to draw. liquid from a sump tank l4 through a suction conduit I8 and deliver the same through a delivery conduit I8. A bypass conduit 20 returns to the'tank any oil delivered by either pump which is bypassed by the internal control valves at any time. The delivery conduit i 8 supplies pressure to a pair of hydraulically-actuated drilling heads 22 and 24 from which exhausting fluid is returned to tank through a conduit 26.

The drilling heads and their actuating and control mechanism per se form no part of the present invention, and they are intended as merely examples of one type of mechanism which may be used to control by an interlock circuit teh single-cycle control mechanism hereafter to be described.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred form of the present invention is clearly shown.

In the drawing:

Figure 1 is a diagrammatic view of a power transmission system incorporating a preferred form of the present invention.

Figures 2 and 3 are enlarged views showing the single-cycle control mechanism in cross section in different positions of the parts.

, Figure 4 is a fragmentary sectional view on line 4-4 of Figure 1.

' Referring now to the drawing, the invention is there illustrated as applied to the control of a rotary table indexing mechanism used with a machine tool such as a multiple-head drilling machine. It will be understood that the invention may be readily utilized for other purposes where a predetermined cycle of operation is to be accomplished of which the machine tool indexing mechanism is merely an example.

Briefly, the heads 22 and 24 are hydraulically actuated under the control of well-known rapid,

, same as the heads start downwardly on a work- A suitable prime mover, such as an electric mg cycle. 1

The fluid delivered by pump i2 is also utilized operate an indexing table drive and control mechanism which receives fluid through a branch delivery conduit 38. Conduit 38 extends to a pressure port 40 of a fcun-way stop-and-go valve 42. The latter has motor supply and return ports 44 and 46 which are connected by conduits 48 and 50, four-way reverse valve 52 and conduits 54 and 56 with a rotary fluid motor 58. Valve 42 also has a tank return port 60 and a drain port 62 which are connected to tank by a conduit 64. The port 60 communicates with the conduit ,64 through a foot valve or back-pressure valve 66 of well-known construction and arranged to remain closed until a predetermined pressure builds up at the port 60.

The valve 42 has a spool 68 which, when in the position shown in Figure-1., blacks the ports 44 and 46 as well as the port 40. When the valve is moved to the right, port 40 is gradually opened to port 44, and port 46 is gradually opened to port 60, the graduation being determined by V- shaped notches I formed in the spool. The spool 68 is thus the member which controls operation of the rotary motor 58. The latter drives by means of bevel gearing a rotary work table- I2 on which work may be positioned for operation upon by the heads 22 and 24. Thus, the table I2 may be driven to carry the workbetween three indexed positions, one of which is a loading and unloading position and the other two of which bring the work beneath the heads 22 and 24. Depending upon the tooling in use on the respective heads, it may be desirable to rotate the table 12 in one direction for one type of tooling and in the opposite direction for another type of tooling. For this purpose the valve .52 may be shifted to reverse rotation of the table whenever the tooling is changed.

Beneath the table I2 there is formed a cam I4 (see Figure 4) adapted to cooperate with a roller I6 carried by a stem 18 of the valve spool 68. The cam I4 is provided with three depressions, such as the one in which the roller I6 lies, and on either side of each depression has a rise portion 86 terminating in a circular portion 82. Beneath the cam I4.there is formed a shoulder 84 in which three tapered recesses 916 are provided for the reception of the tapered end of the stem 18 which thus forms a locking pin to lock the table in the indexed position.

The stem I8 may carry a cam 88 arranged to close a normally-open limit switch 90 which may be connected in series with the starting push button for the heads 22 and 24, thus preventing initiation of head movement whenever the stem I8 is retracted from the recess 86.

For thepurpose of shifting the spool 68 to the right and starting a cycle of table indexing movement, the spool 68 carries at its rightl'and end an enlarged piston 92 having a tapered portion 94 adapted to rest on a seat 96 formed in a hollow piston 98. The piston 98 is slidable in stepped bores I00 and I02 formed in an end cap I04 secured to the righthand end of the valve 42. The cap I04 also includes an end plate I06 positioned adjacent the right end of valve 42 and having a central bore within which the spool 68 is slidable. The piston 98 is biased to the left by a spring I08 andis slidable relative to the enlarged piston portion 92 in the direction separating seat 96 from tapered portion 94. The chamber formed by the piston 98 and bore I02 communicates with the tank conduit 64 through a branch H0.

Branching from the delivery conduit 38 is a conduit I I2 which admits pressure fluid continuously to the righthand end of bore I00, thus creating a constant bias on the piston 92 toward the left as well as on the piston 98.

Also branching from .the delivery conduit 38 is an interlock circuit II4 which extends in series through a spring-closed, manually-operated, starting valve H and through the valves 34 and 36. The interlock circuit terminates at the end cap I04 in two branches. Branch 6 leads directly to the bore I02 in a position where it is closed by the piston 98 whenever the latter lies in the position shown in Figures 1 and 2. Branch II8 leads to the central bore of member I06 at a point therein where the valve spool 98 slightly to the right.

In operation, with the pump I2 running and with the parts in the position illustrated in Figure 1, the delivery of pump I2 being blocked at will close the passage whenever it is moved panels 28,- valve 42 and valve H5, it will be completeiy bypassed through the internal valve mechanism of the pump maintaining a prede termined pressure in the conduit 38. When it is desired to start a cycle of operation, the valve II5 may be manually opened momentarily .to admit pressure fluid through interlock circuit II4, valves 34 and 36 being open at this time, and through branch II8 to the lefthand end of cylinder I02. Piston 88 accordingly moves to the right, and, since seat 96 is in engagement with the tapered portion 94, it carries with it the piston 92 and spool 68, thus retracting the stem 18 from recess 86 as well as retracting roller I6 from its recess in cam I4. Y I ,This movement continues until vthe piston 9 abuts the shoulder at the end of bore I02 as shown in Figure 3. Since the area at the right end of piston 92 is larger than the area of the seat 96, the pressure in the left end of bore I02 cannot lift the piston 92 off the seat, and the spool 68 remains in this position leaving the roller I6 spaced from the cam 14 at a point where the final part of the rise portion 80 will contact the roller after some movement of the table I2. This position of valve spool 68 opens port 44 to port 40, and port 46 to port '60, thus admitting pressure fluid through conduits 48 and 54 to the motor 58 from which it returns through conduits 56 and 50 to the tank conduit 64. The valve 66 maintains a predetermined back pressure on the motor 58 which causes the delivery line pressure to be maintained at a value where the small volume alone of the combination pump I2.is utilized.

As the cam I4 rotates to the point where rise portion 80 contacts roller 16, the valve spool 68 is moved. further to the right to the dotted line position illustrated in Figure 3. This lifts the piston portion 94 off from the seat 96 permitting the oil in the left end of bore I02 to pass through the seat 96 and out conduit IIO to the tank. The fluid pressure acting on the annular area at the right end of piston 98 and also the spring I08 causes the piston 98 to quickly shift to the left, thus again closing the branch conduit H6. Branch conduit II8 was closed as spool 68 moved to the right and remains closed at this time.

It will be noted that, before cam I4 pushed the spool 68 farther to the right, any accidental or intentional reopening of valve H5 would be harmless because the admission of pressure fluid to the left end of bore I02 can shift pistons 92 and 98 no farther. Likewise, after the piston 98 has been reset by the action of cam I4 opening the passage through the piston and seat 96, the interlock conduit H4 is blocked at both branches H6 and H8.

As the table I2 continues to rotate, the roller I6 rides down the incline of the next rise portion permitting spool 68 to gradually shift to the left under the pressure bias on piston 92 thus decelerating the motor 58 by means of the throttling grooves I0. As the roller I6 rides down into the next notch and the stem II drops into the recess It, the table is again locked both mechanically and hydraulically, and piston portion 84 again seals the seat 9!. Not until this happens does the'spool 60 open the branch passage III e to admit of restarting a cycle by actuation of valve HI. With the table thus locked, the working heads 22 and It may be actuated in the usual way by manually starting a cycle oi operation. The limit switch 9| prevents starting a cycle at any time while the table I! is in motion. During.

the working cycle oi the heads 22 and 24, the interlock circuit is blocked by the valves 34 and II, thus preventing another indexing cycle until both heads have returned to their stopped position.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A hydraulically-operated, single-cycle, conthe piston for another cycle, and means controlled jointly by the piston and the member for blocking said conduit after the piston is reset and until the member is returned to stop position.

2. A hydraulically-operated, single-cycle, control mechanism comprising a member shiftable between a. stop position and-a run position, a piston movable relative to said member and arranged to shift the member from stop to run position, a control conduit for directing fluid to operate said piston and shift said member toward run position, means constantly urging said member toward stop position, additional meansfor moving said member further in the same direction that the piston moves it, a valve controlled by said further movement of said member for relieving pressure from the piston to thereby reset the piston for another cycle, and means including a branch conduit controlled by the piston and a second branch conduit controlled by the member for blocking admission of fluid pressure to the piston after it is reset and until the membeer is returned to stop position.

3. A hydraulically-operated, single-cycle, control mechanism comprising a member shii'table between a stop position and a run position, a piston movable relative to said member and arranged to shift the member from stop to run position, a control conduit for directing fluid to operate said piston and. shift said member toward run position, means constantly urging said member' toward stop position, additional means for moving said member further in the same direction that the piston moves it, a valve controlled by said further movement of said member for relieving pressure from the piston to thereby r'eset the piston' for another cycle, means controlled by the piston for blocking said conduit when the piston is reset, and means including a valve controlled by the member for reopening said conduit when the member isreturned to stop position.

DAVID V. SMYTH.

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